THURSDAY, July 31, 2014 (HealthDay News) -- With the World Health Organization reporting that the death toll in the West African Ebola outbreak has risen to 729, the U.S. Centers for Disease Control and Prevention on Thursday issued a travel warning forthe region.

The "Level 3 travel advisory" urges that all non-essential travel to the affected countries -- Guinea, Liberia and Sierra Leone -- be avoided.

"The bottom line is that Ebola is worsening in West Africa," CDC Director Dr. Tom Frieden told reporters in a press briefing.

He said the travel advisory will allow those countries to focus on the outbreaks without worrying about new people coming into the region, while keeping air travel open to people who are headed to the countries to provide medical aid.

He also said that the outbreak has been bad in part because these countries haven't dealt with Ebola before and weren't prepared for it.

In the meantime, putting a halt to the epidemic is "not going to be quick. It's not going to be easy. But we know what to do," Frieden said. He said that the CDC is sending 50 additional experts to the region over the next month.

In another precautionary measure, Frieden said the CDC will be assisting in efforts in the affected countries to prevent Ebola-infected people from boarding planes. If such incidents do occur, protocols will be put in place to identify sick passengers, alert those they may have come into contact with and, if necessary, quarantine people at risk.

At this point, there are no plans to screen passengers arriving in the United States from West Africa for Ebola, the CDC said. "It is important to note that Ebola is not contagious until symptoms appear, and that transmission is through direct contact of bodily fluids of an infected, symptomatic person or exposure to objects like needles that have been contaminated with infected secretions," the CDC said in a news release.